The present invention relates in general to new and improved automatic closures, in particular to a closure which uses a pliant curtain to block the flow of air through a door opening.
Self-closing doors are well known in the art. For certain types of applications adjacent areas need to be isolated from each other, primarily for the purpose of limiting the passage of air therebetween, e.g. where such air may carry fumes and odors, or where it is desired to block the flow of air for the purpose of slowing down temperature equalization between the two areas.
One of the required attributes of self-closing doors is that the doorway in which they are used be easily cleared in order to allow traffic between the two areas, e.g. to permit the passage of people or loaded carts and dollies in either direction through the doorway. Prior art automatic closures which serve the primary purpose of blocking the transfer of air through a door opening frequently employ a solid door. For the purpose intended, the latter type of construction is more permanent, and hence costlier than is warranted under the circumstances. Further, since such closures sustain frequent damage as a result of load traffic in both directions, they need to be frequently replaced. The true cost of such a replacement includes not only the expense of the door alone, but also the cost of removing and replacing a relatively permanent structure.
Although the prior art has recognized that curtains of the proper material adequately serve the purpose of blocking the passage of air through a door opening, satisfactory closures employing such curtains have not been available heretofore. In general, existing arrangements using air-blocking curtains employ two curtain halves fastened to the lintel above the doorway in partially overlapping relationship down the center of the doorway. People and loads transiting the doorway pass between the curtain halves by spreading apart the overlapping curtain portions.
Such an arrangement is unsatisfactory for a number of reasons, primary among which is the fact that it provides a poor air barrier. Inevitably a gap is formed between the two halves through which air can pass. Further, air drafts or the like can readily waft aside the relatively light weight curtain material so as to unblock large portions of the doorway.
Further, if the two curtain halves are affixed to the lintel in a manner where they overlap at the center of the doorway, the curtain will not part easily in its upper portion. Thus, tall objects passing through the doorway often encounter resistance from the curtain. Under these conditions, the possibility of damage to the curtain, particularly in the vicinity of the lintel where the strain on it is likely to be high, is greatly enhanced.
Since the curtain is usually permanently fastened to the lintel in the arrangement described, its replacement, once damaged often consumes an undue amount of time. Thus, heretofore available air barrier curtains are not only prone to damage, but their cost is effectively increased due to the difficulty encountered in replacing and installing them.